Amplifiers have typically used an output drive stage formed by two series connected transistors of opposite conductivity. Bipolar amplifiers often use an output stage having an NPN transistor with a collector connected to a positive power supply connected in series with a PNP transistor having a collector connected to a negative power supply. Positive and negative fifteen volt power supplies are commonly used in connection with bipolar amplifiers. The output voltage is not able to vary a full fifteen volts as the voltage drop across each transistor of the output stage, V.sub.BE, is approximately 0.6 volt and prevents a full range output voltage swing. When a large power supply voltage is used, lack of a full range of output voltage is typically not a problem. However, if the power supply voltage range is much smaller, such as five volts, the lack of full output voltage range may be very limiting in some applications.
In MOS circuits, one of the most common power supply voltage specifications is plus/minus five volts. The ability to provide an output voltage which can vary substantially over the entire power supply voltage range remains important. However, since the voltage range is ten volts, the output does not typically need to be able to vary the full ten volts. As MOS circuits advance, more circuits are being designed for a single low voltage power supply voltage such as five volts. Therefore, the maximum output voltage attainable is five volts or less. The output voltage range problem is aggravated further in MOS circuits because MOS field effect transistors typically have a gate to source voltage drop, V.sub.GS, of one volt or more. Thus when an N-channel MOS transistor is connected in series with a P-channel MOS transistor between five volts and a ground potential, the maximum output voltage variation may be no greater than three volts. In high current drive applications, the low transconductance of an MOS transistor further increases the V.sub.GS of the MOS transistor which only further reduces the output voltage swing. An output stage which uses a P-channel MOS transistor connected to a positive power supply in series with an N-channel MOS transistor connected to the negative power supply provides improved output voltage swing as opposed to having the N-channel MOS transistor connected to the positive power supply. However, the quiescent current thru the output stage is difficult to control resulting in varying power dissipation, and stability problems may exist when this structure is used with a differential amplifier stage.